import {elt, range, removeChildren, removeChildrenAndAdd} from "./dom.js"
import {ie, ie_version} from "./browser.js"

// Detect drag-and-drop
export let dragAndDrop = function () {
    // There is *some* kind of drag-and-drop support in IE6-8, but I
    // couldn't get it to work yet.
    if (ie && ie_version < 9) return false
    let div = elt('div')
    return "draggable" in div || "dragDrop" in div
}()

let zwspSupported

export function zeroWidthElement(measure) {
    if (zwspSupported == null) {
        let test = elt("span", "\u200b")
        removeChildrenAndAdd(measure, elt("span", [test, document.createTextNode("x")]))
        if (measure.firstChild.offsetHeight != 0)
            zwspSupported = test.offsetWidth <= 1 && test.offsetHeight > 2 && !(ie && ie_version < 8)
    }
    let node = zwspSupported ? elt("span", "\u200b") :
        elt("span", "\u00a0", null, "display: inline-block; width: 1px; margin-right: -1px")
    node.setAttribute("cm-text", "")
    return node
}

// Feature-detect IE's crummy client rect reporting for bidi text
let badBidiRects

export function hasBadBidiRects(measure) {
    if (badBidiRects != null) return badBidiRects
    let txt = removeChildrenAndAdd(measure, document.createTextNode("A\u062eA"))
    let r0 = range(txt, 0, 1).getBoundingClientRect()
    let r1 = range(txt, 1, 2).getBoundingClientRect()
    removeChildren(measure)
    if (!r0 || r0.left == r0.right) return false // Safari returns null in some cases (#2780)
    return badBidiRects = (r1.right - r0.right < 3)
}

// See if "".split is the broken IE version, if so, provide an
// alternative way to split lines.
export let splitLinesAuto = "\n\nb".split(/\n/).length != 3 ? string => {
    let pos = 0, result = [], l = string.length
    while (pos <= l) {
        let nl = string.indexOf("\n", pos)
        if (nl == -1) nl = string.length
        let line = string.slice(pos, string.charAt(nl - 1) == "\r" ? nl - 1 : nl)
        let rt = line.indexOf("\r")
        if (rt != -1) {
            result.push(line.slice(0, rt))
            pos += rt + 1
        } else {
            result.push(line)
            pos = nl + 1
        }
    }
    return result
} : string => string.split(/\r\n?|\n/)

export let hasSelection = window.getSelection ? te => {
    try {
        return te.selectionStart != te.selectionEnd
    } catch (e) {
        return false
    }
} : te => {
    let range
    try {
        range = te.ownerDocument.selection.createRange()
    } catch (e) {
    }
    if (!range || range.parentElement() != te) return false
    return range.compareEndPoints("StartToEnd", range) != 0
}

export let hasCopyEvent = (() => {
    let e = elt("div")
    if ("oncopy" in e) return true
    e.setAttribute("oncopy", "return;")
    return typeof e.oncopy == "function"
})()

let badZoomedRects = null

export function hasBadZoomedRects(measure) {
    if (badZoomedRects != null) return badZoomedRects
    let node = removeChildrenAndAdd(measure, elt("span", "x"))
    let normal = node.getBoundingClientRect()
    let fromRange = range(node, 0, 1).getBoundingClientRect()
    return badZoomedRects = Math.abs(normal.left - fromRange.left) > 1
}
